Primary outcome
PTSD Symptom Severity
For the studies included in the meta-analyses, the earliest study was performed in 2014, while the most recent study was performed in 2023. The median sample size across the studies was 36 participants per study. The median of the mean participant age was 37 years (ranging from 29 to 50 years).
Post-intervention (weeks)
8 studies provided data for PTSD symptom severity and contributed 9 effect measures to the PTSD symptom severity meta-analysis. The forest plot for PTSD symptom severity is presented (Extended Data).
Figure 3: Meta-analysis of the effects of exercise on PTSD symptom severity.
The meta-analysis found no significant difference in PTSD symptom severity between exercise and comparison groups (SMD = -0.08, 95% CI -0.24 to 0.07). Low heterogeneity was found as suggested by the prediction interval which is only slightly wider than the confidence interval.
Subgroup Analyses and Meta-regressions
We explored whether heterogeneity could be potentially explained by differences in study-level characteristics using subgroup analyses and meta-regressions. The following characteristics were explored as sources of heterogeneity for the primary outcome, PTSD symptom severity:
Exercise intensity (moderate intensity or high intensity)
Specific exercise type (aerobic or anaerobic or mixed)
Exercise augmented by treatment as usual (TAU)/therapy (exercise only or exercise + therapy/TAU)
Intervention length (weeks)
Subgroup analysis by exercise intensity
There was no significant difference in PTSD symptom severity between studies with moderate intensity and those with high intensity exercise groups (see Figure 4). However, visual inspection of the forest plot suggests the effect is larger in the high intensity exercise subgroup.
Figure 4: Sub-group analysis of the effects of exercise on PTSD symptom severity by exercise intensity
Subgroup analysis by specific exercise type
The were no significant difference in PTSD symptom severity between studies of aerobic exercise, anaerobic exercise, or mixed (see Figure 5).
Figure 5: Sub-group analysis of the effects of exercise on PTSD symptom severity by specific exercise type
Subgroup analysis by exercise alone or tau/therapy augmented by exercise.
There was no significant difference in PTSD symptom severity outcome between studies of exercise alone and therapy/TAU augmented by exercise (see Figure 6). However, visual inspection of the forest plot suggests the effect is larger for exercise alone compared with an inactive comparison group than for the studies that augmented psychotherapy and TAU with exercise.
Figure 6: Sub-group analysis of the effects of exercise on PTSD symptom severity by exercise alone or TAU/therapy augmented by exercise
Meta-regression by intervention length
Overall, there is no strong evidence that the intervention length affected the treatment effect. The meta-regression analysis yielded a coefficient of 0.02 (95% CI: -0.01, 0.05).
Figure 7: Meta-regression of the effects of exercise on PTSD symptom severity by intervention length
Sensitivity Analyses
We examine the robustness of the findings for the primary outcome by excluding studies with high risk of bias. 3 studies included in the meta-analyses were rated as low or some concerns. When restricting the analysis to studies with moderate or low risk of bias, the effect of exercise on PTSD symptoms severity is SMD = -0.06 (95% CI: -0.27 , 0.14). For reference, the main effect size for the primary outcome is SMD = -0.08 (95% CI: -0.24 , 0.07), so the results do not change substantially.
Figure 9: Meta-analysis of the effects of exercise on PTSD symptom severity when excluding studies with high risk of bias
Reporting bias
The forest plot below shows the meta-analysis results of the primary outcome ordered by the precision of the studies. It seems that smaller studies showed larger effects favouring the intervention.
Figure 10: Forest plot of the meta-analysis results of the primary outcome ordered by the precision of the studies
Synthesis Without Meta-analysis
Meta-analysis could not be conducted for three studies addressing the
primary outcome of PTSD symptom severity (Crombie et al., 2021a; Greene
& Petruzzello, 2022; Powers et al., 2015). Two of the studies did
not report outcome data for PTSD symptom severity post-intervention
(Crombie et al., 2021a; Greene & Petruzzello, 2022). The third study
did not provide sufficient data to include in the meta-analysis (Powers
et al., 2015).
Powers et al. (2015) examined the efficacy of adding moderate-intensity
aerobic exercise before prolonged exposure (PE) in reducing PTSD
symptoms. The participants who underwent PE plus exercise experienced a
greater reduction in PTSD symptoms (d = 2.65, SE = 0.92). compared to
the group that received PE only. This outcome was observed after the
12-week intervention.
Risk of bias for the PTSD symptom severity outcome
The results of the risk of bias assessment per domain and study for the primary outcome, PTSD symptom severity is presented below in Figure 2 of the Extended Data. Nine studies reported PTSD outcome data post-intervention. Two studies did not report PTSD outcome data (Crombie et al., 2021a; Greene & Petruzzello, 2022). Five of the nine studies had an overall high risk of bias, three had some concerns, and only one was had low risk of bias. High risk of bias was mainly due to deviations from intended intervention (D2)(Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b), missing outcome data (D3)(Rosenbaum et al., 2015; Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b), and selection of reported results (D5)(Voorendonk et al., 2023; Young-McCaughan et al., 2022).
Figure 2 Results of the risk of bias assessment per domain and overall